Depending on which webinar you choose to watch, you might find a link to download its source code package. Concerning PI AF SDK, you might want to check this webinar which has a source code package for you to download.

vCampus Live! 2012 had a hands on lab for PI AF SDK. If you're interested, the Visual Studio solution for the hands on lab is included in the download package. Note: as the package includes all the hands on lab from vCampus Live 2012, it's quite large.